I understand where you are coming from Graps.
I used to get bent out of shape when some of my items went for below what I anticipated but then I realized, Its an item I could afford to donate and any money raised is a bonus.
If I had an item I felt would get a better price on the classifieds, maybe I would consider selling it in the "off season" and just making a monetary donation to St Jude.
In the end,its for the kids and anything we can raise is better than thinking about what we could have raised. Its spilled milk at that point.
I like Izzy's idea and one year I bought an item back. It would have cost me more to ship it than to double the top bid so thats what I did.